# Talk:Samples and permutations

From Free Pascal wiki

ANother example, not using 2 arrays, but only one, maybe:

```
type
TIntegerDynArray= array of Integer;
{
Returns an array of aSize random integers without duplicates ranging from
aFrom (inclusive) to aTo (exclusive).
- aFrom and aTo must be positive integers
- aTo must be > aFrom
- aSize must be <= aTo - aFrom
- if either of these conditions is not met, an empty array will be returned.
}
function RandomArray(aFrom, aTo, aSize: Integer): TIntegerDynArray; overload;
var
i, j, temp, Range: Integer;
begin
Range := (aTo - aFrom);
if (aFrom < 0) or (aFrom >= aTo) or (aSize > Range) then
Exit(nil);
SetLength(Result, Range);
for i := Low(Result) to High(Result) do Result[i] := aFrom + i;
// Use te Sattolo algorithm to shuffle the array
// https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#Sattolo.27s_algorithm
i := Length(Result);
while i > 0 do
begin
Dec(i);--~~~~
j := Random(i);
temp := Result[i];
Result[i] := Result[j];
Result[j] := temp;
end;
if (aSize <> Range) then
SetLength(Result, aSize);
end;
function RandomArray(aFrom, aTo: Integer): TIntegerDynArray; inline; overload;
begin
Result := RandomArray(aFrom, aTo, (aTo - aFrom));
end;
function RandomArray(Range: Integer): TIntegerDynArray; inline; overload;
begin
Result := RandomArray(0, Range, Range);
end;
```

- Thanks for providing this alternative example. I expect it to be more memory-efficient than my code. This may be especially beneficial in low-memory situations and embedded systems. It doesn't allow, however, for replacement. So, it may depend on the intended use and platform which algorithm to prefer. --Jwdietrich (talk) 14:18, 21 November 2020 (CET)